ENGLEWOOD, Colo. -- The Denver Broncos' defense is a leaky faucet.
It's a maddening drip, drip, drip that just keeps happening no matter how much tinkering, tightening and talking you do to fix it.
But one consistent problem over the past two seasons is stopping the opposing tight end.
"The tight ends, we haven't fixed that yet," is how Broncos coach Vance Joseph has put it already this season.
Consider it a work in progress. Over the past 18 games it's gone from A (Andrews) to almost Z (Witten) as tight end after tight end, regardless of age, experience or résumé, has romped through the Denver defense. It's beyond a trend at this point, and it's definitely on the front burner because the next one in line is Kansas City's Travis Kelce.
Kelce has three career games with more than 130 yards receiving, and two of those have come against the Broncos over the past two seasons -- 160 yards on Christmas night in 2016 and 133 the day before Halloween last season.
"We face good ones almost every week it seems like," Broncos linebacker Todd Davis said. "That's always a concern ... that's been one of the ways offenses come after our defense at times. We always want to do a good job with that."
Last season, tight ends Jason Witten -- who is now an analyst on Monday Night Football and will be on hand when the Broncos host the Chiefs -- plus Kelce, Charles Clay, Evan Engram, Trey Burton, Julius Thomas, Tyler Croft and Vernon Davis all had touchdown receptions against the Broncos. And three weeks into this season, the Broncos have surrendered a 100-yard game to a tight end -- Seattle's Will Dissly had 105 yards on three receptions with a touchdown in the opener.
This past Sunday, Ravens rookie Mark Andrews, who had all of six receptions coming into the game and no receptions longer than 12 yards, had a 30-yard catch-and-run through the heart of the Denver defense. Andrews later had a 29-yard effort on a third-and-8 that moved the ball to the Broncos' 4-yard line.
"We had times we didn't keep them from what they wanted to do," cornerback Chris Harris Jr. said. "And once quarterbacks find something they're going to keep going at it until you stop it. Doesn't matter what it is."
Joseph has talked about the difficulty of the "athletic matchup" today's NFL tight ends present. Many of these tight ends are like jumbo slot receivers, too big for safeties to manage and far too fast for most linebackers, with hands like a go-to guy in almost any offense.
And the Chiefs line Kelce up almost anywhere in the formation. The Broncos have seen Kelce in a variety of places in the motion-heavy Chiefs attack, and it makes it difficult to slow him down at the line of scrimmage because he's often starting his route out of a cluster of receivers.
Once an untouched Kelce gets into his route, the Broncos -- and most of the NFL -- struggle to find the right player to shadow him well enough to keep the ball out of his hands.
"We just need that combination of pressure and coverage," linebacker Von Miller said. "We've been close where we get pressure sometimes and the coverage isn't all the way there or the DBs cover everything up and we don't get the pressure ... we're close to getting that together."
The Broncos have tried safety Justin Simmons -- whose athleticism was on full display against the Ravens when he leaped over the line to block a field goal -- on Kelce, with some good results and some not so good. Linebacker Brandon Marshall has taken his turn at times, and even Miller has found himself in the passing lane in front of Kelce.
Rookie linebacker Josey Jewell made a coverage play down the field against the Ravens' Andrews, but Kelce is a far more difficult matchup in those downfield situations. Kelce already has two 100-yard games this season -- 109 against the Steelers and 114 in Week 3 against the 49ers -- as the pedal-to-the-metal Chiefs lead the league in scoring (39.3 points per game).
"Those are the kind of physical mismatches for a lot of safeties and definitely for a lot of linebackers," Joseph said. "You need a plan where you treat a player like that like a wide receiver, as far as where you put the help. And always you have to rush the passer, speed the quarterback up back there. It's not just one guy or one thing, you have to get a lot of things in place because those kind of players demand it."